docs: def _load_ontology(self, filename, preview_mode=False):
          """
          Loads an ontology
  
          Unless preview_mode=True, it is always loaded from the local repository
          note: if the ontology does not have a cached version, it is created
  
          preview_mode: used to pass a URI/path to be inspected without saving it locally
          """
          if not preview_mode:
              fullpath = self.LOCAL_MODELS + filename
              g = manager.get_pickled_ontology(filename)
              if not g:
                  g = manager.do_pickle_ontology(filename)
          else:
              fullpath = filename
              filename = os.path.basename(os.path.normpath(fullpath))
              g = Ontospy(fullpath, verbose=True)
          self.current = {'file': filename, 'fullpath': fullpath, 'graph': g}
          self.currentEntity = None
          self._print_entity_intro(g)